Do you prototype before building an app or a website?


Many uses but it’s only available for Mac, not open source, and not free.
Another good one is which can be used online therefor works on any platform.

I prefer cross platform and open source tools so I found and I am curious what others are doing. Do some of you skip the prototyping phase completely? I assume if the team is small (1-3 devs), it’s less needed.